PROJECT 3: SYSTEMS BIOLOGY MULTI-OMIC STUDIES OF HEALTHY AGING IN COMPANION DOGS ABSTRACT Aging is an extremely complex phenotype, involving many genes and a large array of environmental factors. Moreover, these determinants of aging do not operate independently but rather interact through a complex and highly intertwined web of molecular processes and functional pathways. To fully understand how genetic and environmental variation lead to variation in aging and age-related disease, one must therefore incorporate these processes and pathways to create a more comprehensive, biologically realistic genotype-environment- phenotype map. Until now, genome-wide association studies in human populations have explained little of the substantial natural variation in lifespan and other age-related phenotypes. This Project aims to address this challenge, using the companion dog as a powerful new model of aging, and focusing on several key mechanisms linking genetic and environmental factors to aging phenotypes. Specifically, three key biological domains ? the metabolome, the microbiome, and the epigenome ? will be explored in a set of three complementary Specific Aims. Preliminary work by the investigators, whose combined expertise spans all three domains, and by other researchers, suggests that these domains represent important functional layers through which genetic and environmental variation shapes downstream phenotypic variation in aging and in age-related disease. To systematically characterize the role of these intermediate functional layers, each of the three domains will be rigorously assayed on an unprecedented scale, using state-of-the-art high-throughput `omic' technologies. By combining data from each -omic domain with ancillary information on genetic, environmental, and age-related phenotypic variation, and working closely with the other Cores and Projects of this P01, this Project will identify molecular elements that are affected by genetic and environmental factors, and which, in turn, are associated with age-related phenotypes. Such analyses will pinpoint specific functional pathways connecting genetic and environmental variation to phenotypic variation in aging. Finally, in a fourth Specific Aim, all three -omic domains will be integrated using novel systems biology and network-based approaches to construct a comprehensive, predictive, multi-omic model of aging in natural populations. Notably, this Project's focus on functional domains and the proposed multi-omic, systems level analysis, go far beyond classical genotype-phenotype associations, mapping functional pathways through which genetics and environment impact aging. Combined, the four Specific Aims of this project will therefore not only facilitate the discovery of new aging biomarkers, but will also provide an improved mechanistic understanding of the aging process, ultimately leading to an analytical, clinically relevant model that can improve prediction, diagnosis, treatment, and prevention of age-related disease in dogs. Importantly, findings that arise from this research also have high translational potential, given that dogs and humans share a common environment, disease burden and attendant risk factor of age.